freebie:~ 746> cat baz
use warnings;
if( 5 == undef ) { 1 }
if( 5 == "undef" ) { 1 }
freebie:~ 747> perl baz
Argument "undef" isn't numeric in numeric eq (==) at baz line 3.
Use of uninitialized value in numeric eq (==) at baz line 2.